Thermostatic switches



Sept. 17, 1963 w. HjMoKsU ETAL 3,104,296

THERMOSTATIC SWITCHES Filed May 11. 1959 6 Sheets-Sheet 2 frz veia to nsf; Wal ter HNazsu, Herzig avzj'vsez;

W. H. MOKSU ET AL THERMOSTATIC SWITCHES sept. 17, 1963 6 Sheets-Sheet 3.

Filed May ll. 1959 54 f6 ze "2@ Je &\\\\\\ \\\\\\vL74 WaZerJMakJ-sa, l Herz@ ava'd Einstein,

Igyzz Sept. 17., 1963 w. H. MoKsU ET AL 3,104,296

THERMosTATIc SWITCHES Filed May 11, 1959 6 Sheets-Sheet 4 fvzzfenam'; WaZterMorau,

Sept. 17, 1963 w. H. MoKsu ETAL 3,194,295

THERMOSTATIC SWITCHES Filed May l1. 1959 6 Sheets-Sheet 5 In vezzons'; Walter H. Malaga, Henry avzfdlfvstezz,

Sept. 17, 1963 w. H. MoKsU ETAL 3,104,296

THERMosTATIC SWITCHES Filed May 11. 1959 e sheets-sheet e B/META L [n1/2z ons Walter ff. Mosu, Henry avz'd Einstein,

af MO5@ Mgg.

United States Patent O 3,104,296 TPMGS'IATIC SWITCHES Walter H. Mohan, Attleboro, and Henry David Epstein,

Cambridge, Mass., assignors to Texas Instruments Incorporated, Dallas, Tex., a corporation of Deiaware Fiied May 11, 1959, Ser. No. 812,528 34 tlaims. (Cl. 200-113) The present invention relates to thermostatic switches, and more particularly, to small thermostatic switches. Although not limited thereto, with regard to more specific features, the thermostatic switch of the instant invention is especially suited and particularly well adapted for protective use in connection with apparatus involving substantial magnetic elds (stray and otherwise), such as encountered in motors, transformers fluorescent ballasts, inductive coils, and the like. It is to be understood, however, that the invention is not limited to such protective use mentioned above, but may -be used wherever found applicable.

It is one object of the instant invention to provide a thermostatic switch means which is simple in structure, adapted for miniaturization, inexpensive to manufacture and reliable in operation.

It is another object of the instant invention to provide a thermostatic switch which is adapted for controlling circuits of devices having magnetic lields, stray and otherwise.

It is yet another object of the instant invention to provide a thermostatic switch adapted for controlling circuits of devices having magnetic fields (stray and otherwise) wherein such a switch is provided with means adapted to avoid, or a-t least minimize, failure due t action in such fields.

It is yet another object of the instant invention to pro'- vide ya switch of the class described which, when used in locations involving magnetic tields, will closely maintain a predetermined desired operating temperature.

It is yet another object of the instant invention to provide a thenmostatic switch which is adapted for miniaturization so as to be conveniently inserted into the small spaces directly adjacent the heated parts of motors, transformers, fluorescent ballasts, inductive coils and `the like, to which heating parts a temperature response is to -be made by the switch.

It is yet another object of the instant invention to provide a thermostatic switch means which is safe 4and reliable in operation and is easily and simply calibrated.

Among further objects of the instant invention are the provisions of a thermostatic switch which is heat and current sensitive, durable, accurate, compact, which is versatile and susceptible to varying electrical ratings, which embodies a minimum number of parts and which is si-mple and economical to assemble and manufacture.

Other objects will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplied in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which several of various possible embodiments of .the invention are illustrated:

FIG. 1 is a top plan view with parts broken away of one embodiment of the instant invention;

FIG. 2 is a sectional View of the thermostat illustrated in FIG. 1 taken on line 2-2 of FIG. 1;

FIG. 3 is a sectional view taken on line 3 3 of FIG. 2 with epoxy omitted for clarity of illustration;

ice

FIG. 4 is a sectional view taken on line 4 4 of FIG. 2;

FIG. 5 is a fragmentary enlarged sectional view similar to FIG. 2 showing the snap-acting thermal element in a contacts-open position;

FIG. 6 is a top plan view of the upper terminal of the thermostat illustrated in FIGS. 1 and 2;

FIG. 7 is a side view of the upper terminal illustrated in FIG. 6;

fFIG. 8 isa top plan view of a spacing header employed in the switch illustrated in FIGS. 1 and 2;

FIG. 9 is a Ifront elevational view of the header shown in FIG. 8;

FIG. 10 is a cross-sectional view taken on line 10-10 ofiFlG. 9;

FIG. 1l is a top plan view of the lower terminal of the thermostatic switch illustrated in IFIGS. 1 and 2;

FIG. l2 is a front elevational view of the lower terminal shown :in FIG. 11;

FIG. 13 is a cross-sectional view taken on line 13-13 of FIG. 12;

FIG. 14 is a top plan view of an insulating member of the thermostat shown in FIGS. l and 2;

FIG. l5 is a front eleva-tional view of the insulating member shown in FIG. 14;

FIG; 16 is a top plan view of a modified header and insulator member;

FIG. 17 is a front elevational View of the headerinsulator member Shown in FIG. 16;

FIG. 18 is a cross-sectional view taken on line 13- 1S of FIG. 17;

FIG. 19 is a top plan view of the housing or can of the thermostat shown in FIGS. l and 2;

FIG. 2O is a top plan view of a modification of an insulating sleeve which may be employed with the thermostatic switch illustrated in FIG. l and with any of the other species of the therm-ostats to be mentioned below;

FIG. 21 is a sectional view taken along line 21-21 of FIG. 20;

FIG. 22 is a fragmentary sectional view similar to FIG. 2, illustrating a thermostat according to another embodiment of the instant invention;

FIG. 23 is a top plan view of another type of thermal element which may he employed with the thermostat shown in FIGS. 1 and 2;

FIG. 24 is a fragmentary section similar to FIG. 2 of a thermostat incorporating the thermal element illustrated in FIG. 23;

FIG. 25 is a fragmentary sectional view similar to FIG. 2 illustrating a thermostat according to a further embodiment of the instant invention;

FIG. 26 is a fragmentary sectional view similar to FIG. 2 illustrating a thermostat according to yet a further embodiment of the instant invention;

FIG. 27 is a sectional view similar to FIG. 2 illustrating another thermostat according to yet a further embodiment of the instant invention;

FIG. 28 is a left-hand elevational lview -of the thermostatic switch illustrated in FIG. 27; and

FIG. 29 is an exploded perspective view of the thermostatic switch illustrated in FIGS. 1 and 2.

Similar reference characters indicate corresponding parts throughout the several views of the drawings. Dimensions of certain `of the parts as shown in the drawing have been modified and/or exaggerated for the purposes of clarity of illustration.

Thermostatic switches are frequently employed in the circuits of motors, transformers, iiuorescent ballasts, and other forms of energy-translating devices vfor prevention of overheating and burn out of the windings or other parts, both when this heating is due to excessive current flow or to excessive ambient temperature rise. Since the heat and current sensitive thermostat of the instant invensequent rapidly repeated 'arc strikes.

tion is usually inserted in small spaces within intricately i transformer or the like, (4) provides safe failure for excessive short-circuiting current, (5 will be versatile and susceptible to varying electrical ratings, and (6).is small enough and of convenientshape to be inserted into the usually small intricately'shaped spaces available in such parts.

It lhas been Yfound `that thermostatic switches which heretofore may have been reliable in non-magnetic locations may become unreliable and even lfail in magnetic fields of substantial intensity. When Ia thermostat is cmployed Ain a magnetic'eld, especially a thermostat of a snap-acting disc type, any arcing which may be :formed by the quick break of contacts, is intensely magnied |because of its presence in the magnetic field. In certain *orientations of the thermostat in the magnetic eld, the arcing is directed toward the calibrated snap-acting element which generally has its high-expansion layer on the side closest to the xed contact, and exposure of thehighexpansion side and/ or its non-develop-able dimpled portion tothe arcingV willtend to destroy the temperature calibration of the device. switches ,are operative in a magnetic eld, the are sometimes formed fupon opening is frequently pushed bythe magnetomotive force so as to strike along the surface of the snap-acting -bimetal causing a temperature rise due to the arc itself which is not the temperature rise in the apparatus against which protection is desired. Therefore, after one or more arc strikes duringa rrepetitive opening and closing protective functioning of the switch, not only may the calibration of the Switch change, but it may change inconsistently. r[the parasitic temperature rise due to the action of the arc builds up -to a high value if rapid Furthermore, when such n 4 f ample, of Monel, tin-plated cold rolled steel or stainless steel. Can l2 may be'formed, lfor example, of steel, aluminum, or copper. Upper terminal 2li includes closely spaced and substantially parallel portions 24 and 26, which are disposed rin reduced section f4 of can l2. As best seen in FIGS. 2 and 5, closely spaced parallel portions 24 and 26 sandwich and mount therebetween in cantilever fashion and in electrically conductive relationship, end 33 of thermal element 3o. Portions 24 and 2o of upper terminal 2li and end 33 of thermal element 30 are provided respectively with aligned apertures 27, `28

opening and closing action of the switch occurs'lwith con- Moreover, physical deterioration and annealing due to the I,burning action of the arc on the bimetal of the snapacting thenmostatic element tends to change its operating characteristics, particularly if these affect the dirnpled or non-developable area responsible `for snap action'. In addition, arcs due to short circuits may occur which, if not promptly broken, may cause complete burn out of the contacts and the bimetal of the switch.

The present invention, in each of the embodiments,`

avoids or at least minimizes the above-stated difficulties 'and results in a very small and reliable switch of substantial versatile capacity, which may lbe'inserted ina wide variety lof locations where required.

Referring now to the drawings, there is illustrated in ing or "can l2 has la rear closed-end portion 14 of reduced cross-sectional area anda forward open-ended portion 16 which is adapted to slidably receive a thermostat assembly to'lbe described below. Housing or can Vl2 is a metallic, heat and electrically conducting material.

Thermostat luis provided with ian upper electrically conducting terminal 20. Upper terminal 20 extends rear wardly fromV the open end `lo of c an lv2yinto the reduced portion f4 of can l2 and includes `a return portion lgen- ,V erally referred to by numeral 22, which extends forwardly toward'theopen end of the housing and terminates just rearwardly of a stationary termin-al 70. ,Up-per terminal Ellis electrically conducting and may be formed, lfor ex- United States Patent 1,448,240 of March 13,1923. As

illustrated in FIGS.Y 2 Land 5, the highexpansion metal is on Vthe bottom side as :at 34, that is on the concave side, of dished areaV 32 as seen in FIG. 2. The lowexpansion layer 36 is on -theupper side as seen in FIGS. 2 and 5. The thermos-.tatiev snap-acting element 3l) basically is one of the `sic-called inherent differential type of snap-acting thermostats in which the portion 32 comprises a non-developable surface. The temperature at which snap-acting thermostat element 30 will snap when `heated and when cooled is at least in part determined by the amount of dish of the dished area 32 and theshape of the area. may be formed of conventional thermostat material, such as for example, bimetal or trimetal. Snap-acting element 39 is-provided with a contact '3S which may :be formed of a conventional material such `as silver or a silver alloy which is secured to the free end of snap-acting thermal element 30 by rivet 40. Surface portion .62 of upper Y termina-l 20, which isV directly above contact 3S `or thermal element 30, serves as a stop which riveted head 40 will strike when theV thermostat is subjected to excessive shortcircuiting currents, and remain fused thereto due to melting and splattering ofthe material of the contact thus affording an open circuit or safe'failure'of the device.

Thermostatic element 30, in addition to being sandwiched and Vclamped between porti-ons 24 and 26 of upper terminal 2i), is also secured `as by welding at 42 and 4,4

to upper terminal 2li to insure a positive electrical conf nectiontherebetween and for other purposes Ato be described below. In practice, the'upper terminal 20 and thermal element Sli are secured together |as described above asa separate` subassemblyY and slidably inserted into can l2 with other components to be ydescribed below in final assembled relation. Y

Since thermal element 30 is generally a relatively thin strip of metal, upper terminal 20 Ym-ust be suiliciently rigid to protect fthe disc or thermal element 30 when the upper terminal thermal element assembly is being inserted into can l2. Upper terminal `20l must also be sufficiently rigid to remain deformed when the can l2 vis bent during calibration, which will be described in greater detail below. Upper terminal 2li is secured to an electrically conducting lead `46 `adjacent the open portion lo of can l2. UpperV termina-1 Ztl is provided with wire clinchtype ylocking means comprising wing portions 47 and 4S which are best seen in FIGS. 6 and 7. V-llectrical lead 4o is clinched between wing portions 47 and 48 which provides la low-cost and simple fastening method, eliminating a costly and tedious welding operation. For fast wire insertion, terminal 2li, `in practice, may be fabricated in long strip form, rolled onto reel-s and then fed into a wire clinching machine. Upper lterminal 2@ is also provided with a notched portion 49 which will rupture at its neck when lsubjected to excessive current. Notched portion 49 also positions other parts of -the thermostatic device in correct assembled relationship toy The thermo'static, snap-acting element 3l) the thermal element, which tfeature will abe discussed in greater detail below.

Surface portion Sil* of upper terminal 20 adjacent bent portion 52 which is adjacent dished portion 32 serves as a stop for dished portion 32 to bear 'against and snap from a contacts-closed position as seen in full lines in FIG. 2 to a contacts-open position as seen in the dashed Ilines in FIG. 2 and full lines in FIG. 5. Surface portion 50, in bearing against the convex side of dished portion 32, when ther-mal element Sti is in a contacts-closed position, acts as `a limit stop and cooperates with the securing means, welds 42 and 44, to prevent thermal element 30 from creeping to a contacts-'open position. By anchoring the cantilever end 33 of thermal element 3G in a positive manner, no creep action to a contacts-open position can take place and snap action is assured. Otherwise, in a condition of gradual temperature change, thermal element 30, as is characteristic of `such dished snap-acting elements, may creep to .open fthe contacts prior to its snap-action in spite of the presence of the ydirnpled or dished portion 32 and surface portion 50. Consequently, it is seen that both surface area 50 and the securing means, welds 42. and 44, co-operate to prevent snap- -acting thermal element 30 from acting as a creep-type device in creeping to a contacts-open position from a contacts-closed position.

Surface portion 54 of upper terminal 20 adjacent bent portion 56 is spaced from surface portion 5t) to provide clearance for snap-acting element 30 to snap act in response to predetermined temperature and current conditions. Surface portion Sie also serves as a limit stop for and lco-operates with the securing means, welds 42 and 44, to prevent snap-acting element 3d from creeping to a contacts-closed position from a contacts-open position without the occurrence of snap action. As best seen in FIG. 5, dished portion 32 when in the contactsopen position, bears against surface 545. Surface 54 serves as a fulcrum point against which dimpled portion 32 bears and snaps. The clearance spacing between sur- [faces Sti and 54 is important in assuring both that the snap-acting disc 30 will have sufficient clearance to snap act but not so much clearance that would permit the snap-acting disc to operate as a creep-type device.

To obviate the aforementioned dangers in regard to arc strikes, portion I69 of upper terminal 26 adjacent bent portion 51S is spaced from -thermal element 30 and is located adjacent the contact 3S. Portion `60 has substantially the same potential as thermal element 3) and acts as an arc control grid to attract the arcing and thereby protect thermal element 361 from exposure to the arcing.

Referring now to FIGS. 2 and 5, lower or stationary Iterminal 70 provides a stationary contact which may take the form of a -conventional contact material and comprise, for example, an upper layer of silver or silver l alloy 72 bonded or otherwise adhered to a base layer 74 which may comprise, for example, cold rolled steel. The upper surface of silver layer 72 is serrated as by a plurality of grooves 73` and 75 which extend normal to each other, as shown in FIGS. l\1-l3, to prevent an open circuit due to dirt and light contact pressure. Stationary terminal 70, as upper terminal 20, is provided with a notched portion 76 which will rupture when excessive short-circuit current is incurred. Notch 76 also positions stationary terminal 7d in `direct assembled relation to other components as will be more fully described below. Stationary terminal 70 is also provided with a Wire clinch-type looking means for electrical connection to lead 78, which is or may be substantially similar to that of the upper terminal 20 and may comprise wing portions 80' and S2 which are adapted to be bent and clinched around wire lead 718. Stationary terminal 70 can also be fabricated and secured to its electrical lead in the same manner as that described above for upper terminal Ztl.

Stationary terminal 70 is maintained in sp'aced electrically insulated relation to can l2 by insulator 36 as best seen in FIGS. 2 and 5. Insulator A8,6 may be constructed of a conventional insulating material such as, for example, a strip of silicone or steatite. In the practice of the instant invention, steatite is preferably employed so as to provide a device which has no organic or resinous type parts which can cause build up of undesirable gases and ultimate failure of the device, a feature which will be described in greater detail below. Insulator `86 is also provided with a notched portion S8, as best seen in FIGS. 14 and 15, for a purpose to be described below.

As best seen in FIGS. 2F5, insulator 86 has a length and width which is less than that of stationary terminal 70. Lower or stationary terminal 79, when in lixed assembled relation to insulator y86, overlaps insulator S6 along three edges `92, A94 and 96, as best seen in FIGS. 2, 3 and 4. Overlapping edges 92, 94 and 96 of lower terminal 70 provide arc shadow, which is effective to constitute a |gap in and prevent the creation of a lowresistance current path between lower terminal 70 and electrically conducting can l2. Such a low-resistance electrical current path could be formed by particles of silver or other material of the contact 38 of thermal element 30i which may be thrown off as the contact makes and breaks quickly. l

The upper terminal ZO-thermal element 3() assembly, stationary terminal 70 and insulator 86 are aligned and maintained in a tixed, spaced, electrically insulated, assembled relation to each other within can 12 by header means 160. Header means 109, as shown in FIGS. l-S and `8-10, includes notched portions 102 and 104 which are complementary in shape to and mate and intert respectively, with notched portions 49 of upper terminal 20, and notched portions 715 of stationary terminal 7th and notched portions yS8 of insulator 86 so as to tixedly position the respective parts in proper assembled relation and to insulate upper terminal 2@ from stationary terminal 7i) as shown. Header means 100 may be lfor-med of any suitable electrically insulating material. However, in the practice of the instant invention, it is preferable that header member be of a ceramic steatite material so that the thermostat does not have any organic or resinous type of parts which can cause build up of gas or failure, as will be described in greater detail below. Ceramic steatite header 100 serves as an arc barrier for arcing which may occur, such as referred to above in regard to arc control grid 60. If the thermostats position in a magnetic tield is such as to lcause arcing in a direction toward the ceramic header 100, the header will resist the arcing. Because of the steatite construction of header 100, arc deterioration will not occur, and there is no danger of creating a lowresistance path between the terminals, as would be the case with a header constructed of a phenolic resin or other thermosetting material. Header is further provided with a transversely extending slot or groove 10S, which provides arc shadow and prevents formation of a low-resistance current path which could be formed by silver or other material of the contact 38 of snapacting element 30, which are thrown olf as the contacts break quickly. As such particles are thrown oi, they will strike the upper vertical and horizontal sides Il@ and 112 of slot 108 and not the lower inside corner 1G14, which inside corner constitutes a gap in a low-resistance current path which might be created as described above. Header 100 is also complementary in shape to the interior cross-sectional shape of can l2 and is dimensioned so as to provide a sliding tit therebetween when the -thermostatic assembly is slidably inserted into can l2. 'Ihis sliding fit serves to maintain the thermostatic assembly in txed assembled relation within can IZ and also forms a stop or a seal to prevent epoxy 112i?, which will be described below, from leaking into the interior of the can into the thermostatic assembly.

FIGS. 16-18 illustrate a modified header and insulator arrangement generally referred to by numeral Ullfl'fi'. Header mit is similar to header itltl, except that it includes integrally formed therewith, an insulating member Se corresponding to insulating member 8o. Header 00 is or maybe constructed of substantially the same electrically insulating material as Vthat'o-f mit'. Header lftl, as header 110th includes notches itil and i104 which kare complementary in shape to and are adapted to mate and interfit with, respectively, notched portions 49 of upper terminal Ztl and notched portions 7 6 of stationary terminal "70. Header member 160" is provided with a `longitudinally extending slot or groove ldd' which is substantially identical to and performs the same function as slot 103 lof header 160 to` provide arc shadow. Insulating portion 86' may be constructed of a length andV width which is less than that lof stationary terminal '7d so as to'provide substantially the `same arc shadow effect discussed above in connection with insulator S6. Header 160 can'be employed whereV applicable in each of the embodiments lof FIGS. 1v-l522, 24, 25 and 26.

Can for housing lf2 is a metallic envelope formed of a conventional electrical and beat conducting material such as, for example, steel, copper lor aluminum. It is preferred, however, to employ'steel. In each embodiment tof the instant invention, since the upper terminal is also of steel and the can 12 is in close proximity thereto, the advantageous result of greatly minimizing the effect tof leakage fiux in a magnetic field on arcs pro` duced by making and breaking of the contacts is o tained. Providing the can i2 of an electrically conducting metallic material such as ldescribed above has distinct advantages over a housing or can provided of phenolic contact pressure between contacts 38 and 7d. There is a definite relationship between the amount of bend and inc-rease tor decrease in resulting contact pressure, and such adjustment can be made as desired. There is also a definite relationship between contact pressure and the operating temperature and current Vcharacteristics of the snap-acting disc. For example, at a lcentain contact pressure, the disc willy snap at certain definite temperature and current conditions. Therefore, by varying the amount of bend in area BA of can 12, the snap-acting thermal element can be calibrated to 'operate at predetermined temperature and current conditions. This simple calibration method provides an inexpensive means to calibrate land render the device effective for a wide variety of diverse applications covering a wide range of temperature and current oper-ating characteristics. During calibration, the anchorage ofelement by welds 42 and 44, which are illustrated as lying within fulcr-um or resinous material. lt has been Ifound that a snap-acting thenmostat provided with ay housing lof'a'phenolic or resinous material may be unsatisfactory when such snap action is magnified many fold and when such arc strik-es the housing which, if formed of a phenolic or tacts created Iby the material of the deteriorated phenolic housing. rllherefore, by providing a housing of an electrically conductive metallic. material described above,L this problem is avoided. Further, since theV metallic housing is also heat conductive, the bimetallic member which is heat sensitive, more accurately reects the thermal conditions. Y Y

After the components of the thermostatic assembly have been assembled into fixed relation and have been slidably inserted into can l2, an electrically insulating layer of adhesive compound 120; which may, forexample, take the form of an epoxy potting compoundyis introduced into the open end lo of can 12. The potting compound l2@ serves to mount,hermetically seal and maintain the thermostat sublassembly in fixed assembled position within the can or housing 12. Y

The thermostat of the instant invention can be quickly and easily calibrated fby bending a predetermined portion of the reduced end 14 of can l2 after the entire thermostat is in final assembled condition. Portion BA, as shown in PlG. 2, .is bent to calibrate the snap-acting thermal element 30 for response to predetermined temperature and current conditions. When portion BA of can l2 is bent, for example, in a countenclockwise direc-V tion, there is a rotation of the snap-acting thermal ele,

ment 3ft about fulcrum` area FA resulting in a change in area FA, kplay an impohtant role by preventing variation in and maintaining constant the predetermined clearance space between surface portions Sti and 54 while still perjmitting rotation of the rdisc for calibration purposes.

Welds 42 and 44 are located at the outer .edges of the thermal element 30 so as not to interfere with ythe initial temperature setting ofthe dished portion 312i.

Thermostat dll, as well as each of the-additional modifcations to be described below, may be provided with a surnounding electrically insulating high dielectric sleeve 13d las `seen in FIGS. l1 4 and 29. Sleeve 130 is generally cylindrical in shape. Sleeve 13) may be formed of any conventional electrically insulating materials, such as, vfor example, Mylar which is a highly durable, transparent, water repellent lm of polyethelene terephthalate resin. FIGS. 2() tand 2l illustrate a modification of a sleeve 140' which might be employed. As cleanly seen in FIGS. 20 and 2l, sleeve Mb is complementary in shape to that of can l2 and includes a reduced portion 1412 s which corresponds to reduced portion 114 of can l2.

- thermostat is in a magnetic field. The arc created by the of sleeve 130. s FIGS. 23 and 24 illustrate another embodiment of the instant invention. Thermostat lil as illustrated in FIGS. 23 and 24 is substantially identical with the thermostat 10 illustrated inVFlGS. land 2 and differs only in the Sleeve'lftl may be for-med of the sanrematerial as that kconstruction of the thermal element 3G and its mounting to portions 24 and 26 of upper terminal 20, as will be described below. Thermal element 3b is a creep-acting type element and generally comprises as relatively .thin elongated thermostat metal strip. Thermostatic element 30 is provided with an aperture 28 which is for the same purpose as and corresponds to aperture 2.8 of snapacting .thermal element 30.. Creep-acting thermal element Sil is also provided with Contact 33' which is riveted as at 4u to creep-actingY thermal element 3h. The highexpansion layer of the thermostat metal is on thelower side 34' and the low expansion layer k36 is on the upper side. Creep-acting thermal element Btl is both heat and current responsive. The heat mass of can l2 and upper terminal Ztl contributes to causing'thermal element 39 to creep act. lf greater current sensitivity is desired, the upper terminal ZVcan be formed of a high electrical resistance material and electrically insulated from can l2 (not shown) so that upper terminal 2u will effectively act a-s a heater for creep-acting thermal element ll. It should be understood thatupper terminal 2d, for snapacting thermal element Sil, could also be madefof a high f electrical resistance material and electrically insulated -or welded to portions 24 and 26 of upper terminal 2h as was snap-acting thermal element 3ft., Thermostat l0 is or may be substantially identical in all other respects to thermostat l@ illustrated in FIGS. l and 2 and is attended by substantially all of the advantageous results attending the thermostat 10. With creep-type thermal element 39', the clearance spacing between surfaces Si) and 54 are not as critical as they are with the snap-acting type thermal element 3i), and consequently, upon bending or deforming of reduced portion 14 of can 12 during calibration, if the surface portions t) and 54 should change their clearance slightly, this slight change would be insigniiicant since there is very little relative motion in the creep-type element. However, Vthe securing means, welds 42, and 44, may be desirable for a positive electrical connection between upper terminal and the thermal element. Thermostat l0' may be assembled in substantially the same manner as that described for thermostat l@ above.

FIG. illustrates a further modification of the instant invention. Thermostat 200 is substantially identical to thermostat iti illustrated in FIGS. 23 and 24 and differs mainly in that upper terminal Zita is formed of a thermostatic metal. Upper terminal 20a is constructed of a thermostatic bimetal with the high expansion layer on the outside as represented by HES in the drawing. The low-expansion side of the bimetal is on the inside as represented by LES in FIG. 25. Thermal element Stia is similar to thermal element and differs mainly in that the high-expansion layer is on the upper side as at 36a and the low-expansion is on the bottom side 34a. Although the thicknesses as illustrated of the upper terminal Zita and thermostatic element 30a have been modified and/ or exaggerated for clarity of illustration, in practice the thermostatic metal of the upper terminal Ziia has a thickness considerably greater than that of the thermostat element 30a. This results in a modified creeptype thermostat. The thermostat metal of upper terminal Zita, since it is relatively thick, heats relatively slowly in relation to the rate of heating of the relatively thin thermostatic element 30a and is therefore relatively slow in thermostatic motion in response to current and heat. This results in affording a temperature differential which is somewhat greater than that attainable by an ordinary creep-acting type thermal element but is still of a magnitude which is smaller than the differential attainable by a snap-acting thermal element such as snapacting thermal element 3i) in the species of FIG. l. As the upper terminal 26a heats up, the lower portion 24a will move up and physically contact thermal element Stia and thereby force thermal element 3tia to move .t0 a contacts-open position. The force with which portion 24a of upper terminal Zta urges thermal element 36a to a contacts-open position is etiective to break apart any contact welds which may have been formed. Thermal element 36a, which has the high-expansion side on the upper side and is considerably thinner than upper terminal 29a when heated by current passing therethrough, tends .to increase Contact pressure until the upper terminal 28a moves in response to increased ambient temperature and heat generated by current passing therethrough causing portion 24a to engage and move thermal element 30a to a contacts-open position. When upper terminal 20a cools sufficiently to permit element 36a to move to a contactsclosed position, the relatively thin thermal element Stia again heats up and the high-expansion material 36a, being on the upper side, causes increased contact pressure, assuring a positive contact. From the above, it is seen that thermostat 200 combines the advantages of an ordinary creep-type thermostat and that of a snap-acting thermostat in that it provides a definite temperature differential, eliminates undesirable creep-type characteristics, such as, of example, radio interference, and yet provides a smaller temperature differential than that generally available with a snap-acting type thermostat. Thermostat 200 enables increased contact life over that ordinarily available with an ordinary creep-type thermostat since thermal element 30a breaks faster and eliminates much of the burning of contacts which ordinarily occurs with the creep-type thermostat which generally have effectively a very small differential, for example, as little as one degree. Except where noted above, thermostat 20)l is substantially identical with thermostat it) in all respects and has substantially all of the advantageous results attainable by .the construction of thermostat lit.

PEG. 26 illustrates yet another embodiment ot the i-nstant invention. Thermostat 3G@ is generally similar to the construction of thermostat l0. Can 302, terminal 316, spacing header means (not shown) of thermostat 3% are or may be substantially identical to can l2, terminal 76, rand header means 16th of Ithermostat 10. Thermostat 36M? is provided with an insulating member 386 such as Se of thermostat lit, as illustrated in FlG. 26, bu-t such may be omitted, if desired. Stationary terminal 316 is shown as being mounted on insulator 386 and electrically insulated from cam 3%2. Thermostat 360 lis provided -with an upper -terminal 304 which `is somewhat similar in configuration to upper terminal 29 of thermostat lt?. Upper terminal 334 is formed of thermostat bimetal and has the high-expansion side indicated by HES in FIG. 26 on the outside layer 3M. The low-expansion side of the thermostatic bimetal is on the inside layer 305. Upper terminal 3h4- includes a lower leg 368. Upper terminal 304 is provided with a contact 310 which is secured to the free end of leg 368 as by rivet 312. Upper terminal 304 is relatively thin and constitutes a creep-type thermal element which is extremely current and heat sensitive. Upper terminal 304 is maintained in spaced electrical insulation lfrom can 302 by an electrically insulating layer of material, such as for example, a conventional insulating sheet material or an adhesive compound 3l4 which may, for example, take the form of an epoxy compound similar or substantially the same as epoxy compound 12? of the thermostats of FIGS. l and 24. Thermostat 36h is a simply constructed device, does not employ an additional thermal element as the embodiments previously described, can be calibrated in the same manner as the embodiments of FlGS. l-24 and 25, `and provides an easily and quickly assembled low-cost thermostat. The remainder of switch 360` is substantially identical with thermostat 1t) with respect to the header and manner of assembly and the epoxy sealing compound at the open end.

FlGS. 27 and 28 illustrate yet a further embodiment of the insta-nt invention. Thermostat 4h@ comprises a can 4:32 somewhat similar in configuration to can 12 of thermostat itl. Thermostat 4% is provided wi-th an upper terminal 464 which may be substantially identical 'with upper terminal 2t) of thermostat 10. Thermostat 400 further includes a snap-acting type thermal element 406 which is or may be substantially identical Ito snap-acting thermostat element 36 of thermostat 16. It should be understood that it is within the purview of the insta-nt invention to also employ a creep-acting thermal element (not shown) which may be similar or identical to creepacting thermostat element 35)" and 36a, respectively, of thermostats l0 and 209. Upper terminal 494 is in electrically conducting relationship With can 402. Exterior terminal 410 is welded as at 4t2 to the exterior of can 492 and is in electrically conducting relationship with upper terminal 464. Stationary terminal 42@ provides a stationary contact .and may take the torm of or be substantially identical to stationary terminal 7d of thermostat 10 and is mounted on .and electrically connected to a current-carrying member 422 which extends outwardly and exteriorly of casing member 402. 'Member 422 is mounted in a glass-to-metal header assembly :generally referred to by numeral 430 which comprises a flanged collar 432 which is complementary in configura-tion to the open-ended portion 431 of cam 402. A glass seal 434 Ifused to flanged collar 432 fixedly mounts and posi-tions current-carrying member 422 .and eectively hermetically seals the open end of can 462. In practice, the upper terminal 4t4-thermal element 4th? assembly is slidably inserted into can 402 and then the glass-to-metal header assembly dt-current-carrying member 422-terminal 420 assembly is lslidably inserted into can 402 and secured thereto `as by heli-arc welding or soldering anged collar 4532 to Ican 402 at 433 so as toeffectively providewa hermetic seal and properly Vplace the'contacts in proper spaced assembled position. Exterior terminal di@ is then secured, as by welding, to can 402. f

From the above, it is seen that thermostat 40) comprises a relatively small number of parts, `and can be si-mply and quickly produced Iand yet can be calibrated in the same manner as each of the embodiments described above.

FIG. 22 illustrates another embodiment of the instant invention.V Thermostat Go, as illustrated in FIG. 22, is somewhat similar to thermostat lt)I as illustrated in FIGS. Vl and 2. Thermostat 'Stili does not employ an upper terminal such as upper terminal 2d of thermos-tat ld. Can '5.432 is a metallic envelope for-med ofla conventional electrical and heat conducting material such as, for example, steel, copper or aluminum.l It is preferred, however, to employ steel in the instant invention for reasons mentioned above in regard .to can l2 of thermo-V stat lil. Thermostat ddii is provided with a bimetallic snap-acting thermal element 530 which includes a dished kor non-developable portion 532 responsible for its snapaction, 4a contact 538 mounted at one end thereof by rivet means 540, a stationary contact 57d and an insulator 586, each of which may be or are Vsubstantially identical, respectively, with snap-acting element 30', stationary ,terminal 70 yand lower insulator 36,- respectively, of thermostat l as illustrated in FIGS. l and 2.y Thermostat 56d also includes a ceramic header meansy oil@ ygenerallyv similar to ceramic header means lttl except thatceramic header means `@ad does not include notched portions for the reception of `an upper terminal. In all other respects, ceramic header means 6th) is or may be subs-tantially' identical with ceramic header means 100 of thermostat lll. Can Sti-r2 includes a closed-end portion of reduced cross-sectional area 594. Reduced section Slidincludes porti-ons 506 and 59S which sandwich and mount therebetween in cantilever fashion and in electrically con-l ductive relationship, one end 505 of snap-acting thermal element 53d in ya manner similar to the mounting .of thermal ele-nient 3d by portions 24 and 26 of upper terminal 2t) of the 4thermostat ltl. Y 505 of snapsacting elementdil is secured to portions 506 an 5% as by welding or crimping as at S07. Surface portion Slt) adjacent bent portion '512 of can 562 corresponds in function to sur-face portion Sti of upper terminal Ztl :and ser-ves as a stop -for ldished portion 532 to bear against and snap from a contacts-closedposition to a contactsopen position. Surface S10, in bearing against the convex side of dished .portion 5312 when thermal element 53E)1 is in a contacts-closed position, :acts las a limit stop to prevent snap-acting thermal element 530 fromy operating as a -creep device in creeping to a contacts-y open position. The securing means 567 (-welding, crimping or the like), also `cto-operates to prevent snap- Cantilever mounted end Y v' as welds d2 and 44, to maintain such clearance during bending -for calibration purposes.

Portion `Siti of cam 502 serves as an arc control grid and serves substantially the same Vfunction as portion 6) of upper terminal `20 of thermostat lll. Thermostat 500 is further provided with .a terminal '517 which is welded or -otherwise secured in electrical conducting relationship to can S02 as seen in FIG. 22. A Y

Surface portion 5l5 of can 5&2 corresponds to sur-face portion `62 of upper terminal Ztll andk serves substantially the same' function. The riveted head Smit) will strilce surface portion 515 when the thermostat is subjected to excessive Yshort-circuiting [currents and will remain -fused thereto due to melting and Vsplattering of the material of the contact, thus altording an open circuit or safe failure of the device. After snap-acting thermalelement 53h` and stationary con-tact 57d, insulator 58d and header 60a have been assembled within can S02, a layer of potting compound 682, which is or may be substantially` identical with the epoxy compound 12d of thermostat lil is applied to Y seal land maintain the thermostatic subassembly in proper assembled relation within can 502. Y

A creep-type thermal element such as shown in FIG. 23 could be substitutedfor snap-.acting thermal element S30. Also, integral header .and lower insulator shown in FIGS. 16-18, if properly modiflied by omitting the upper notch litli, could be Vsubstituted for headermeans 600;

Thermostat 500 is attended bysubstantially 'all the :advantages of thermostat lll and additionally provides the advantages of eliminating the upper terminal -thereby to acting disc 53d trom `operating as a creep-type thermal y element assuring snap-acting inthe same manner as the attachment by -Welds d2 and da described `above with respect to thermostat lill. inner surface portion 514 of can Sitz adjacent bent portion ISlo corresponds in function to surface vportion 5d of upper terminal 20` and erves substantially the same function. Surface portion dit serves las-a lful-crum point against which tdimpled portion 532 bears and snaps from .a k.contacts-open to a n contacts-closed position. SurfaceV portion 514, in cooperation with secu-ring means 507, is effective to prevent Y theV s-napacting disc from operating as a creep-type device to creep to a contacts-closed position. As is the case with the spacing between surf-aces 5t) :and 54, the

spacing between surfaces Sl@ and 514 is also important in assuring that the snap-acting disc 530 will have sufficient clearance to snap act but not so much clearance permit construction of a less expensive device.

It should be understood that in each of the embodiments described above, the can or louter` housing can be electrically insulated from both terminals if desired or required by specific applicati-ons of the thermostat.

ln addition to the advantages set forth above, the i-nstant invention provides la thermostat which comprises individual subassemblies which :can be mass produ-ced 'and quickly .and inexpensively .assembledfinto operative .position; a devi-ce with which miniaturization is alforded because of the relatively small number of parts and a device which is easy to rcalibrategland very versatile inns-e in a wide rrange of diverse applications.

ln view of the above, it vvill be ,seenV that the several objects of the invention are achieved and -other advan- Ytageous results attained.

As many changes could be made in .the above constructions without departing `from the scope of the invention, it is intended that all matter contained in the above devscription or shown in the accompanying drawings, shall be interpreted las illustrative .and not in a limiting sense., and i-t is also intended that the appended claims shall cover Vall such equivalent variations as come within the true spirit and scope of the invention.

We claim:

l. A thermostatic switch comprising a metallicfhousing having a closed end, said housing having therein a iirst electrically conducting terminal Vspaced from a second electrically conducting terminal, said iirst terminal promeans adjacent the other end thereoi` providing cantilever support for said thremostatic plate means, insulating header means maintaining said terminals in spaced electrically insulated relation, Vsaid closed end of said housing having a portion thereof so shaped to provide a pair of opposed interior surfaces thereof in close proximity to the outer surfaces or said second terminal portions for alb-1,29%

i .13 engagement therewith, whereby calibration of said thermostatic pla-te means when assembled in said switch structure may be effected externally of said switch structure by deforming said portion of said housing.

2. A thermostatic switch comprising a housing, said housing having therein a iirst electrically conducting terminal spaced from a second electrically conducting terminal, said rst terminal providing an electrical contact, a creep-acting bimetal element supporting a contact thereon adjacent one end thereof for movement into and ont of engagement with said rst-named contact at predetermined temperature and current conditions, said second terminal having portions in engagement with and in electrically conducting relation to said creep-acting bimetal element adjacent the other end Ithereof providing cantilever support therefor, insulating means maintaining said terminals in spaced electrically insulated relation, said portions of said second terminal engaging said creepacting bimetal element comprising thermostatic material of greater thermal mass than that of said creep-acting bimetal plate and having a plurality of layers having unequal coeflicients of thermal expansion with the layer thereof having the lowest coeicient of thermal expansion closest to said creep-acting bimetal element.

3. The switch of claim 2 land .wherein the high-expansion side of said creep-acting bimetal element is on the side furthest away from said rst terminal.

4. A thermostatic switch comprising a metallic housing having an open and a closed-end portion and formed of heat and electrically conductive material; said housing having disposed therein a first electrically conductive terminal spaced from a second electrically conducting terminal, said tlirst and second terminals having portions accessible exteriorly of said housing for electrical connection in an electrical circuit; said first terminal providing an electrical contact; said second terminal being formed of thermally responsive composite material and including a flirst portion extending into said closed end portion of said housing and a second portion interconnected with said first portion and extending toward said open end of said housing; said first and second portions defining a U-shaped member; said second portion comprising a creep-acting bimetal element mounting a contact thereon adjacent the free end thereof for movement into and out of engagement with said yfirst-named contact at predetermined ambient temperature and current conditions, land electrically insulating header means disposed in said open end of said housing maintaining said first and second terminals in spaced electrically insulated relation and means electrically insulating said second terminal from said housing.

5. A thermostatic switch comprising a housing having an open end; said housing also including a closed end of reduced cross-sectional area, said housing having therein first and second electrical contacts, snap-acting thermostatic means supporting said second contact thereon adjacent one end thereof for movement into and out of engagement with said first contact at predetermined temperature and current conditions, an electrically conducting terminal having portions disposed within and closely spaced to a pair of opposed interior surfaces of said reduced, closed end of said housing, means securingv said portions in electrically conducting engagement Vwith said thermostatic means adjacent the other end thereof providing cantilever support therefor, said snap-acting means having a non-developable portion responsible for its snapaction and being movable between a cont-acts open and a contacts closed position, said terminal including further portions adjacent opposite sides of said non-developable portion and spaced to provide sufficient clearance to permit snap-action of said non-developable portion but to prevent said thermostatic means from moving to one of said contacts open and closed positions prior to the ocourrence of snap action, said reduced closed end portion of said housing being deformable as by bending, externally 14 thereof, for effecting calibration of said snap-acting thermostatic means and said means securing said iirst-named portions to said thermostatic means co-operating to prevent variation in the clearance between said spaced further portions adjacent said non-developable portion during calibration.

6. A thermostatic switch comprising an elongated housing having an open end, said housing having therein a rst electrically conducting terminal spaced from a second electrically conducting terminal, said iirst terminal providing an electrical contact, thermostatic plate means supporting a contact thereon adjacent one end thereof for movement into and out of engagement with said firstnamed contact `at predetermined temperature and current conditions; said second terminal having portions in electrically conducting engagement with at least two surfaces of said thermostatic plate means adjacent the other end thereof providing cantilever support therefor; insulating header means maintaining said terminals in spaced electrically insulated relation adjacent the open end of said housing, said header means comprising a glass-to-metal header 1mounting one of said terminals thereon and secured to and sealing the open end of said housing.

7. The thermostatic switch recited in claim 6 and wherein said thermostat plate means comprises a snapacting thermostatic plate, said plate having intermediate its ends, a nondevelopable portion responsible for its snap action, and means securing said portions engaging said surfaces to said surfaces .at at least one point between said nondevelopable portion and said other end of said thermostatic element.

8. A thermostatic switch comprising a heat and electrically conductive elongated housing having a closed-end portion, said housing having therein a pair of electrical contacts, thermostatic means operatively connected with one of said contacts for movement of said one of said contacts into and out of engagement with said other oontact at predetermined temperature and current conditions, said closed-end portion of said housing having means associated therewithin, extending in electrically conducting engagement with at least two surfaces of said thermostatic means adjacent one end thereof providing cantilever support therefor, terminal means interconnected with and electrically connected with said means associated with said closed end portion of said housing and adapted for electrical connection in an electrical circuit; and means securing said means associated with said closed-end portion to said engaged surfaces of said thermostatic means.

9. A thermostatic switch comprising a metallic housing formed of heat conductive and electrically conductive material; said housing having therein irst electrically conductive terminal means spaced from second electrically conductive terminal means, said first terminal means providing an electrical contact, a snap-acting thermostatic strip member supporting a contact thereon adjacent one end thereof for movement into and out of engagement with said first-named contact at' predetermined temperature and current conditions, said strip having a deformed portion responsible kfor its snap action, said second terminal means having portions adjacent said housing in engagement and in electrically conductive relation with said thermostatic strip adjacent the other end thereof providing cantilever support for said thermostatic strip, insulating header means maintaining said lirst yand second terminal -means in spaced electrically insulated relation, said housing having a portion thereof so shaped to provide interior surface portions thereof overlying the outer surface of said portions of said second terminal means whereby calibration of lsaid thermostatic strip when assembled in said switch structure may be effected externally of said switch structure by deforming said portion of said housing.

l0. A thermostatic Switch comprising a heat and electrically conducting elongated metallic housing having a i closed-end portion, said housing having therein a pair of electrical contacts, Van elongated .fbimetallic snap-acting thermostatic member operatively connected adjacent one end thereof with one of said contacts for movement of said one of said contacts into and out of engagement with said other, contact at predetermined temperature iandcurrent conditions, said snap-acting .member having a nondevelopable portion responsible for its snap action, said closed-end portion of said housing having means associn ated therewithin, extending in electrically conducting engagement with at least two surfaces of `said thermostatic member adjacent the other end thereof providing cantilever support therefor, and means securing said means associated with said closed-end portion to said engaged surfaces of said thermostatic member.

"11. An electrical switch comprisinga metallic, heatconductingV tubular casing having an open and a closed Vend section; said switch providing a tirs-t electricallyV conmeans formed of inorganic material disposed in said open end of said casing and maintaining said terminals: in spaced electrically Vinsulating relation; and said header means interiitting wit-hV said open end of said casing to seal the interiorV of said switch against the entry of any sealing materials applied externally of said header means to seal said switch. i p

12. The switch as set forth in claim 11 and wherein the interior surface of said header means is formed of a ceramic material-and the interior surface thereof i-s provided With yat least-one recessed portion'providing for arc shadow.

13. The switch as set forth in claim l1k land wherein one of said first and second termina-ls includes a section of reduced cross sectional area adapted to rupture `and cause an open circuit upon a current flow in excess of a predetermined amountpand said reduced cross sectional areabeing in mating and intertting engagement wit-h said header means.'

14. A thermos'tatic switch adapted for miniaturization comprising a tubular metallic housing; rirst and second electrical contacts within said housing adapted to open andk close a circuit; said switch including an electrically conducting terminal provided with snap-acting' thermally i responsive means operatively connected with said first arranged for operative engagement with, said deformed v portion to prevent said thermally responsive means from moving to one of said contacts open land closed positions prior to the occurrence of snap action, while providing sufficient clearance for snap action of said thermally responsive means. f

15. A thermostatic switch adapted ttor miniaturization y comprisinga Itubular metallic housing; a pair of electrical contacts within said housing adapted to open andY close a circuit; .said switch including an electrically conducting terminal provided with snap-acting thermally responsive meansimountingr one of said contacts for movement into and out of engagement with the other of said contacts at predetermined temperature and current conditions; saidV Y lo thermally responsive means lbeing in intimate heat-transfer relation to said housing and having a deformed portion responsible for its snap acti-on; said thermally responsive means being movable to contacts open and closed positions; said terminal including surface portions ladjacent vand so spaced from said deformed portion that said deformed porti-on will engage said surface portions to prevent said thermally responsive means from moving to one of said contacts open andclosed positions prior t tothe occurrence of snap action While providing sufficient Iclearance 'for snap action of said thermally responsive means. e y

k16. An electrical switch comprising a heataconducting tubular casing; said casing having disposed therein a` rst electrically conducting terminal spaced from a second electrically conducting terminal; said first terminal providing an electrical contact; an elongated Vthermostatic member supporting a contact thereon adjacent one end and means maintaining Ksaid terminals in spaced electricalp ly insulated relation. I

17. A thermostatic switch comprising-a metallic elongated tubular housinghaving a closed end section; said Vhousing having therein 4a pair of electrical contacts; snapacting thermostatic means mounting-one of said contacts adjacent one end thereof for movement intoand out of engagement with the other of said contacts; said housing being in intimate heat-transfer relation to said thermostatic means; electrically iconducting means associated with said closed end 'section having portions sandwiching `therebetween -the otherend of said thermostatic means providing a cantilever support therefor; said thermostatic means having, intermediate its ends, a nondevelopable portion responsible for its snap actionV and being movable between contacts open 'and closed positions; one of said portions overlying said nondevelopable l portion providing means spaced from-and engageable with said nondevelopable portion .to prevent said thermostatic means from moving to one of said contacts 4open yand closed Vpositions prior to the occurrence of snapaction whilefproviding suilicient clearance for snap action of said thennostatic means.

18. The switch as recited in` claim 17 `and vwherein said portions lsands'viching said'thermostaitic means are in electrically conducting engagement therewith and are formed integrally with said closed end section of said housing.

19. The switch as recited in claim 18 `and wherein said onerot said portions includes -a further portion adjacent said Icontact Icarried by said thermostatic means providing an arc control grid whereby arcs struck between said contacts are deected by said grid from said nondevelopable portion. y

20. The switch Ias recited in claim 18 and said portions of said closed-end portion lofsaid :housing engaging said snap-acting thermostatic means being deformable as by bending, externally thereof, for effecting ,calibration of said snap-acting thermostatic means; and means securing said portions of said closed end section of said housing to saidthermostatic means co-operatingI to prevent vari-ation in the cle-arance between said one portion and said nondevelopable portion during calibration.`

, 21; A thermostatic switch comprising a metallic heatconducting tubular housing; said switch including an electrically conducting terminal and a pair of electrical contacts; an elongated snap-acting thermostatic member supporting Vone of said contacts thereon adjacent one end thereof for movement into and lout of engagement with the other of said contacts at predetermined temperature and current conditions; said snap-acting thermostatic member including a nondevelopable portion therein responsible for its snap action; said terminal having portions d-isposed in electrically conducting relation with and sandwiching therebetween the other end of said thermostatic member, thereby cantilever mounting said member; said terminal further including an elongated part thereof overlying at least a portion of said :thermostatic member and disposed in intimate heat-transfer relation therewith; and said elongated part 4having a substantial electrical resistance and serving as a heating means for said thermostatic member.

22. A thermostatic `switch comprising a metallic elongated tubular housing having a closed end section; said housing having therein a pair of electrical contacts; snapacting thermostatic means mounting one of said contacts adjacent one end thereof for movement into and out of engagement with the other of said contacts; said housing `bei-ng in intimate heat-transfer relation to said thermostatic means; electrically conducting means associated with said closed end section having portions sandwiching therebetween the other end of said thermostatic means providing a cantilever support therefor; said thermostatic means having, intermediate its rends, a non'developable portion responsible for its snap action; one of said portions overlying said nondevelopable por-tion providing an arc control `grid whereby arcs struck between said contacts may be deiiected by the grid away from said nondevelopable portion of said thermostatic means.

23. A thermostatic switch adapted for miniaturization comprising a tubular metallic housing; a pair of electrical contacts within said housing adapted to open and close a circuit; said switch including an electrically conducting terminal provided with snap-acting thermally responsive means mounting one of said contacts for movement into and out of engagement with the other of said contacts at predetermined temperature and current conditions; said thermally responsive means being in intimate heat-transfer relation to said housing and having a deformed portion responsible for its snap action; said thermally responsive means being movable to contacts open and closed positions; said terminal including surface portions disposed in one end of said housing spaced from and engageable with said deformed portion t prevent said thermostatic means from moving to one iof said contacts open and closed positions prior to the occurrence of snap action while providing sufficient clearance for snap action of said thermally responsive means; and said end of said housing being deformable as by bending, externally thereof, for effecting calibration of said snap-acting thermally responsive means.

24. A thermostatic switch adapted for miniaturization comprising a tubular metallic housing having a closed end section of reduced cross sectional area; a pair of electrical contacts within said housing adapted to open and close a circuit; said switch including an electrically conducting terminal provided with snap-acting thermally responsive means mounting one of said contacts for movement into and out of engagement with the other of said contacts at predetermined temperature and current conditions; said thermally responsive means bei-ng in intimate heat-transfer relation to said housing and having a deformed portion responsible for its snap action; said thermally responsive means being movable to contacts open and closed positions; said terminal .including at least a portion thereof disposed in said reduced closed end section of said housing, welded to said thermally responsive means; said termi-nal further including surface portions adjacent and so spaced from said deformed portion that said deformed portion will engage said surface portions to prevent said thermostatic means from moving to one of said contacts open and closed posi-tions prior Ito the occurrence of snap action while providing sufficient clear- 18 ance for snap action of said thermally responsive means; and said reduced closed end section of said housing being deformable as by bending, externally thereof, for effecting calibration of said snap-acting thermally responsive means.

25. An electrical switch comprising a heat-conducting tubular casing; said casing having disposed therein a first electrically conducting terminal spaced `from a second electrically conducting terminal; said first terminal providing an electrical contact; an elongated snap-acting thermally responsive member having a deformed portion responsible for its snap action and movable to contacts open and closed positions; said member supporting a contact thereon adjacent one end thereof for movement into and out of engagement with said vfirst-named contact at predetermined ternperature and current conditions; said second terminal cantilever mounting the other end of said member and being electrically connected thereto; and said second terminal further including an elongated part thereof overlying at least a portion of said member and including surface portions adjacent and so spaced from said deformed portion that said deformed portion will engage said surface portions to prevent said thermally responsive member from moving to one of said contacts open and closed positions prior to the occurrence of snap action `while providing sufficient clearance for snap action of said thermally responsive member.

26. The switch as recited in claim 25 land wherein said casing is formed of electrically conductive material; insulating header means maintaining said first and second terminals in spaced electrically insulated relation; means interposed between and maintaining said rst terminal .and said electrically conductive casing in spaced, electrically insulated relation; and said first terminal having Ia plurality of edges extending beyond and in overlapping relation to said last-named insulating means providing arc shadow.

27. The switch -as recited in claim 26 and wherein said means maintaining said first terminal in spaced electrically insulated relation to said casing is integral with said header means.

28. The switch as recited in claim 17 and wherein said one of said portions includes a further portion adjacent said contacts carried by said snap-acting thermostatic means providing an arc control grid whereby arcs struck between said contacts are deflected by said grid from said nondevelopable portion of said snap-acting thermostatic means.

29. The switch :as set forth in claim 17 and wherein said housing is formed of a steel alloy.

30. A thermostatic switch comprising a metallic elongated tubular housing having an open and a closed end section; said housing having therein first and second electrically conducting terminals; said first terminal providing a first electrical contact; snap-acting thermostatic means mounting a second contact adjacent one end thereof for movement into and out of engagement with said first contact; said housing being in intimate heat-transfer relation to said thermostatic means; said second terminal including portions in said closed end section being electrically connected to and sandwiching therebetween the other end o-f said thermostatic means providing a cantilever support therefor; land glass-to-metal header means mounting said first terminal, maintaining the latter in spaced electrically insulated relation to said second terminal and hermetically sealing said open end of said houslng.

3l. The switch as set forth in claim 10 and wherein said means associated with said closed lend portion is welded to said engaged surfaces of said thermostatic member.

32. A thermally responsive electrical switch comprising a tubular casing having open end and closed end portions; first and second electrically conductive terminals disposed in said casing and each including la portion prol19 i jecting exteriorly of said casing; said iirst terminal providing `a first electrical contact disposed within said cas i ing; said second terminal. including aV portion disposed withinsaid Casing adjacent the closed end lportion there-Y of; Ian elongated thermally responsive bimetallic, snapacting member having a deformed portion responsible for its snap action, said snap-acting member being disposed spaced, opposed elongated'portions disposed in said housing adjacent the closed end thereof, said opposed porwithin said casing and being electrically connected and fixedly secured adjacent one end thereof to said portion of said second Iterminal adjacent said closed-end portion of said casing thereby providing cantilever support for said snap-acting member; said snap-acting member lalso Y mounting anY electrical Contact adjacent the other end thereof for movement into and out of engagement with said first contact; electrically insulating header means distions of said second terminal sandwiching therebetween a portion of said snap-acting member adjacent the other endv thereof providingcantilever support for said snapacting member; said other end portion of said snap-acting member 4being electrically connected and Xedly sepcured to said second terminal; the one of said second terminal portions disposed adjacent the side of said snapacting member supporting said movable contact being dis-V V posed adjacent said deformed portion of said snap-acting member providing (an arc control grid for deecting arcs struck between said first and movable contacts away posed adjacent said open end of said casing and main- Y taining said first and secon-d terminals in spaced electrically insulated relation; and said header means intertting with the open end of said casing to seal the' interior of the switch against the entry of sealing materials applied externally of the header means to seal the switch.

33. The switch as set forth in claim 32 land wherein ysaid snapaacting member is welded to said portion of said second terminal adjacent said closed-end portion of said casing.

34. A thermally responsive electrical switch comprising a tubular casing having an `open and )a closed end, said` casing having therein a rst electrically conductive terminal spaced from a second electrically conductive terminal,V said first terminal having an end portion projecting exteriorly of said casing and providing an electrical contact adjacent another end thereof; asnap-acting thermally responsive member supporting a mov-able contact thereon adjacent one end thereof for movement into `and out of engagement with said first-named contact at predetermined temperature and current conditions, said snap-acting member having a deformed portion responv sible for its snap action, said second terminal having `from said deformed portion of said snap-acting member;

header imeans disposed adjacent the open end of sai-d cas-L ing and maintaining said terminals in spaced velectrically insulated relation, said closed `end of said casing having a portion thereof so shaped to provide a pairof opposed interior surfaces thereof in Vclose proximity toy the outer surfaces of said second terminal portions for engagement therewith,whereby calibration `,of said snap-acting member w1 en lassembled in s-aid switch casing may be effected externally of said switch by deforming said portion ofl said casing.

. References Cited in the file of this patent UNITED STATES PATENTS 2,199,638

Jepson et al Apr. 5, 1960 

10. A THERMOSTATIC SWITCH COMPRISING A HEAT AND ELECTRICALLY CONDUCTING ELONGATED METALLIC HOUSING HAVING A CLOSED-END PORTION, SAID HOUSING HAVING THEREIN A PAIR OF ELECTRICAL CONTACTS, AN ELONGATED BIMETALLIC SNAP-ACTING THERMOSTATIC MEMBER OPERATIVELY CONNECTED ADJACENT ONE END THEREOF WITH ONE OF SAID CONTACTS FOR MOVEMENT OF SAID ONE OF SAID CONTACTS INTO AND OUT OF ENGAGEMENT WITH SAID OTHER CONTACT AT PREDETERMINED TEMPERATURE AND CURRENT CONDITIONS, SAID SNAP-ACTING MEMBER HAVING A NONDEVELOPABLE PORTION RESPONSIBLE FOR ITS SNAP ACTION, SAID CLOSED-END PORTION OF SAID HOUSING HAVING MEANS ASSOCI- 